Pis’ma v ZhETF, vol. 111, iss. 1, pp. 32 - 33

January 10

Optical Kerr nonlinearity of disordered all-dielectric resonant high

index metasurfaces with negative refraction

A. V. Panov¹⁾

Institute of Automation and Control Processes, Far East Branch of Russian Academy of Sciences, 690041 Vladivostok, Russia

Submitted 4 November 2019

Resubmitted 18 November 2019

Accepted 18 November 2019

DOI: 10.31857/S0370274X20010063

In recent years, nonlinear optical properties of all-

The procedure of computation of the real part of

dielectric high index metasurfaces have attracted a sig-

the effective nonlinear refractive index of the monolayer

nificant interest of researchers [1]. For example, silicon

nanocomposites is described in depth in [10]. The sim-

metasurfaces exhibited enhancement of third harmonic

ulation parameters in the present study were same as

generation by several orders of magnitude compared to

given in [5]: the size of the FDTD computational do-

the massive material [2, 3]. The intensity-dependent re-

main was 4 × 4 × 30 μm, the space resolution of the sim-

fractive index is regularly used in designing all-optical

ulations was 5 nm. The examined sample was a disor-

compact switches. As demonstrated in [4], all-optical

dered monolayer comprising the equal numbers of GaP

switching of femtosecond laser pulses passing through

spheres of two radii surrounded by vacuum. As shown

flat nanostructure of subwavelength silicon nanodisks at

in [6], the densely packed bidisperse monolayer of GaP

their magnetic dipolar resonance occurs owing to two-

spheres with the radii r of 77 and 101 nm exhibits the

photon absorption being enhanced by a factor of 80 with

negative refraction at λ = 532 nm.

respect to the unpatterned film. In [5], random monodis-

The evaluation of the effective second-order non-

perse metasurfaces of gallium phosphide (GaP) spheres

linear n_2eff refractive index for the bidisperse mono-

near Mie resonances were shown by three-dimensional

layer of the spheres with volume fraction f = 25.7 %,

finite-difference time-domain (FDTD) modeling to have

r1 = 77 and r2 = 101 nm having negative refraction

an optical Kerr effect exceeding by two orders of in-

index is (6.5 ± 0.8) × 10-15 m2/W which is two or-

tensity that of the bulk gallium phosphide. Moreover,

ders of magnitude larger than that of the bulk gal-

being single negative metamaterials, the monodisperse

lium phosphide. For purposes of comparison, the bidis-

metasurfaces with sphere sizes in the vicinity of the Mie

perse monolayer consisting of spheres of artificial ma-

resonances reveal the inversion of the sign of the second-

terial with n₀ of GaP and n₂ of gallium phosphide

order nonlinear refractive index [5]. The possibility of

with negative sign was modeled: the resulting value of

negative refraction by the disordered metasurface con-

n_2eff = -(6.5±0.7)×10-17 m²/W, that is the negative

sisting of GaP spheres with two radii close to the first

index metasurface does not show the inversion of n_2eff

magnetic and electric Mie resonances was demonstrated

sign.

in [6]. However, until now, the effective Kerr nonlinear-

Then, the optical nonlinearity of the bidisperse

ity of the negative index metamaterials has not been

metasurface during the concentration transition to the

evaluated.

negative refraction state is investigated. The behavior of

In this work, the optical Kerr nonlinearity of ran-

n_0eff through the transition to negative values was stud-

dom metasurfaces having the negative effective refrac-

ied in [6]. Figure 1 illustrates the dependency of the ef-

tive index is investigated using three-dimensional FDTD

fective second-order nonlinear refractive index n_2eff on

simulations at the wavelength of 532 nm. The second-

the volume fraction of nanoparticles in the bidisperse

order nonlinear refractive index is also calculated for

monolayer. At low concentrations of the GaP spheres

bidisperse mixtures with various sizes or concentrations

(f = 8-18 %), the metasurface exhibits the negative

of GaP spheres in proximity to the negative refraction

value of n_2eff due to the inversion of optical Kerr coeffi-

regime.

cient near the electric dipole Mie resonance [5]. For the

higher volume fractions of nanoparticles, n_2eff becomes

positive and has a peak when n_0eff crosses zero. Fur-

¹⁾e-mail: andrej.panov@gmail.com

ther, the effective second-order nonlinear refractive in-

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2020

Optical Kerr nonlinearity of disordered all-dielectric resonant high index .. .

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2020